1. Field of Technology
Exemplary embodiments include a unitary filter tank and/or an underdrain for a filtering a body of water.
2. Brief Discussion of Related Art
Swimming pools often use sand filter units to remove particulate and gelatinous contaminants from pool water. A typical sand filter unit includes a filter tank, a separate base unit upon which the filter tank rests, an underdrain assembly disposed within and towards a bottom of the filter tank, and a water circulation system to circulate water through the filter unit. Once the underdrain assembly is in place within the filter tank, the filter tank is filled with sand, which covers the underdrain assembly. In a typical implementation, pool water enters the filter tank towards a top end via the water circulation system and percolates through the sand to the underdrain assembly, which collects cleansed pool water for recirculation in the pool by the water circulation system.
FIG. 50 is an example of a conventional sand filter tank assembly 5000 having a filter tank 5010 with a separate base 5050. The filter tank 5010 has an opening 5012 at a top end 5014 of the filter tank 5010 and interface structures 5016 at a bottom end 5018. The opening 5012 facilitates communication between an interior and exterior of the filter tank 5010 for the water circulation system. The interface structures 5016 can be configured for mounting the filter tank 5010 on the base 5050. The base 5050 includes interface structures 5052 for receiving the interface structures 5016 of the filter tank 5010. In operation, the filter tank 5010 rests on the base 5050 and is subsequently filled with a filtrate material.
FIGS. 51-55 show an example conventional filter tank manufacturing system 6000 and process for forming the filter tank 5010 of FIG. 50. The system 6000 can include an extrusion head 6100, a mold 6200 operatively coupled to a press 6300, and a blow pin 6400. The mold 6200 can be partitioned into two sections and can be moveable between an open and closed position by the press 6300. To form the filter tank, molten polymer parison 6110 is extruded between the mold sections by the extrusion head 6100 when the mold 6200 is in the open position. Once a sufficient amount of molten polymer parison 6110 has been extruded, the press 6300 can urge the opposing sections of the mold 6200 together so that the mold 6200 is in the closed position. In the closed position, the molten polymer parison 6110 is pinched at the ends of the mold 6200 to form a molten polymer body 6120. The blow pin 6400 can be introduced into the mold 6200 and into an interior area of the molten polymer body 6120 and can blow or force air into the molten polymer body 6120 to expand the molten polymer body 6120 outward towards contoured surfaces of the mold 6200 until the molten polymer body conforms to the mold. The blow pin 6400 can continue to blow air to cool and harden the molten polymer body. Once the molten polymer body 6120 has been sufficiently cooled and hardened, the mold 6200 is opened to release the newly formed filter tank.
With respect to the underdrain assembly of a filter unit, several configuration have been implemented. In one common implementation, a underdrain assembly can have several separate parts that can be coupled to form the underdrain assembly during installation of the underdrain assembly in a filter tank. Reference is also made, for example, to U.S. Pat. No. 5,068,033, the contents of which are incorporated herein by reference for all purposes.